1. Field of the Invention
This invention relates generally to oscillators and, more particularly, to a horizontal oscillator which utilizes an on chip capacitor for use in television receiver systems.
2. Description of the Prior Art
Typical black and white television receivers utilize a horizontal oscillator which generates an asymmetrical ramp signal at a frequency of 15.75 KHz which is the line frequency in the United States. These typical oscillators employ an expensive external capacitor (in the order of 10 nanofarads) and generate a charge/discharge current of approximately 1 milliamp which is derived from a reference current generated by the circuit. With the trend toward single chip television receivers, it would be desirable to integrate the oscillator capacitor on the integrated circuit chip. However, current state of the art integration techniques do not permit integration of capacitors which are larger than approximately 100 picofarads. Utilizing this smaller capacitor would require that the charge/discharge current be reduced to 5 to 10 microamps in order to maintain the oscillator frequency. However, conventional RC oscillators which attempt to define these low currents tend to be variable due to loading effects.